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      <td><p class="toc level1"><a href="docinfo.html">Document Information</a></p>
<p class="toc level1 tocsp"><a href="gexaf.html">Preface</a></p>
<p class="toc level1 tocsp"><a href="gfirp.html">Part&nbsp;I&nbsp;Introduction</a></p>
<p class="toc level2"><a href="bnaaw.html">1.&nbsp;&nbsp;Overview</a></p>
<p class="toc level2"><a href="gfiud.html">2.&nbsp;&nbsp;Using the Tutorial Examples</a></p>
<p class="toc level1 tocsp"><a href="bnadp.html">Part&nbsp;II&nbsp;The Web Tier</a></p>
<p class="toc level2"><a href="bnadr.html">3.&nbsp;&nbsp;Getting Started with Web Applications</a></p>
<p class="toc level2"><a href="bnafd.html">4.&nbsp;&nbsp;Java Servlet Technology</a></p>
<p class="toc level2"><a href="bnagx.html">5.&nbsp;&nbsp;JavaServer Pages Technology</a></p>
<p class="toc level2"><a href="bnajo.html">6.&nbsp;&nbsp;JavaServer Pages Documents</a></p>
<p class="toc level2"><a href="bnakc.html">7.&nbsp;&nbsp;JavaServer Pages Standard Tag Library</a></p>
<p class="toc level2"><a href="bnalj.html">8.&nbsp;&nbsp;Custom Tags in JSP Pages</a></p>
<p class="toc level2"><a href="bnaon.html">9.&nbsp;&nbsp;Scripting in JSP Pages</a></p>
<p class="toc level2"><a href="bnaph.html">10.&nbsp;&nbsp;JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="bnaqz.html">11.&nbsp;&nbsp;Using JavaServer Faces Technology in JSP Pages</a></p>
<p class="toc level2"><a href="bnatx.html">12.&nbsp;&nbsp;Developing with JavaServer Faces Technology</a></p>
<p class="toc level2"><a href="bnavg.html">13.&nbsp;&nbsp;Creating Custom UI Components</a></p>
<p class="toc level2"><a href="bnawo.html">14.&nbsp;&nbsp;Configuring JavaServer Faces Applications</a></p>
<p class="toc level2"><a href="bnaxu.html">15.&nbsp;&nbsp;Internationalizing and Localizing Web Applications</a></p>
<p class="toc level1 tocsp"><a href="bnayk.html">Part&nbsp;III&nbsp;Web Services</a></p>
<p class="toc level2"><a href="bnayl.html">16.&nbsp;&nbsp;Building Web Services with JAX-WS</a></p>
<p class="toc level2"><a href="bnazf.html">17.&nbsp;&nbsp;Binding between XML Schema and Java Classes</a></p>
<p class="toc level2"><a href="bnbdv.html">18.&nbsp;&nbsp;Streaming API for XML</a></p>
<p class="toc level2"><a href="bnbhf.html">19.&nbsp;&nbsp;SOAP with Attachments API for Java</a></p>
<p class="toc level1 tocsp"><a href="bnblr.html">Part&nbsp;IV&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="bnbls.html">20.&nbsp;&nbsp;Enterprise Beans</a></p>
<p class="toc level2"><a href="bnbnb.html">21.&nbsp;&nbsp;Getting Started with Enterprise Beans</a></p>
<p class="toc level2"><a href="bnboc.html">22.&nbsp;&nbsp;Session Bean Examples</a></p>
<p class="toc level2"><a href="bnbpk.html">23.&nbsp;&nbsp;A Message-Driven Bean Example</a></p>
<p class="toc level3"><a href="bnbpl.html"> <tt>simplemessage</tt> Example Application Overview</a></p>
<p class="toc level3"><a href="bnbpn.html">The <tt>simplemessage</tt> Application Client</a></p>
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<p class="toc level3"><a href="">The Message-Driven Bean Class</a></p>
<p class="toc level4"><a href="#bnbpp">The <tt>onMessage</tt> Method</a></p>
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<p class="toc level3 tocsp"><a href="bnbpq.html">Packaging, Deploying, and Running the <tt>simplemessage</tt> Example</a></p>
<p class="toc level4"><a href="bnbpq.html#bnbpr">Creating the Administered Objects for the <tt>simplemessage</tt> Example</a></p>
<p class="toc level4"><a href="bnbpq.html#bnbps">Building, Deploying, and Running the <tt>simplemessage</tt> Application Using NetBeans IDE</a></p>
<p class="toc level4"><a href="bnbpq.html#bnbpt">Building, Deploying, and Running the <tt>simplemessage</tt> Application Using Ant</a></p>
<p class="toc level4"><a href="bnbpq.html#bnbpu">Removing the Administered Objects for the <tt>simplemessage</tt> Example</a></p>
<p class="toc level3 tocsp"><a href="bnbpv.html">Creating Deployment Descriptors for Message-Driven Beans</a></p>
<p class="toc level1 tocsp"><a href="bnbpy.html">Part&nbsp;V&nbsp;Persistence</a></p>
<p class="toc level2"><a href="bnbpz.html">24.&nbsp;&nbsp;Introduction to the Java Persistence API</a></p>
<p class="toc level2"><a href="bnbrl.html">25.&nbsp;&nbsp;Persistence in the Web Tier</a></p>
<p class="toc level2"><a href="bnbrs.html">26.&nbsp;&nbsp;Persistence in the EJB Tier</a></p>
<p class="toc level2"><a href="bnbtg.html">27.&nbsp;&nbsp;The Java Persistence Query Language</a></p>
<p class="toc level1 tocsp"><a href="bnbwi.html">Part&nbsp;VI&nbsp;Services</a></p>
<p class="toc level2"><a href="bnbwj.html">28.&nbsp;&nbsp;Introduction to Security in the Java EE Platform</a></p>
<p class="toc level2"><a href="bnbyk.html">29.&nbsp;&nbsp;Securing Java EE Applications</a></p>
<p class="toc level2"><a href="bncas.html">30.&nbsp;&nbsp;Securing Web Applications</a></p>
<p class="toc level2"><a href="bncdq.html">31.&nbsp;&nbsp;The Java Message Service API</a></p>
<p class="toc level2"><a href="bncgv.html">32.&nbsp;&nbsp;Java EE Examples Using the JMS API</a></p>
<p class="toc level2"><a href="bncih.html">33.&nbsp;&nbsp;Transactions</a></p>
<p class="toc level2"><a href="bncjh.html">34.&nbsp;&nbsp;Resource Connections</a></p>
<p class="toc level2"><a href="bncjx.html">35.&nbsp;&nbsp;Connector Architecture</a></p>
<p class="toc level1 tocsp"><a href="bnckn.html">Part&nbsp;VII&nbsp;Case Studies</a></p>
<p class="toc level2"><a href="bncko.html">36.&nbsp;&nbsp;The Coffee Break Application</a></p>
<p class="toc level2"><a href="bnclz.html">37.&nbsp;&nbsp;The Duke's Bank Application</a></p>
<p class="toc level1 tocsp"><a href="gexbq.html">Part&nbsp;VIII&nbsp;Appendixes</a></p>
<p class="toc level2"><a href="bncno.html">A.&nbsp;&nbsp;Java Encoding Schemes</a></p>
<p class="toc level2"><a href="bncnq.html">B.&nbsp;&nbsp;Preparation for Java EE Certification Exams</a></p>
<p class="toc level2"><a href="bncnt.html">C.&nbsp;&nbsp;About the Authors</a></p>
<p class="toc level1 tocsp"><a href="idx-1.html">Index</a></p>
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<a name="bnbpo"></a><h3>The Message-Driven Bean Class</h3>
<a name="indexterm-2145"></a><a name="indexterm-2146"></a><p>The code for the <tt>SimpleMessageBean</tt> class illustrates the requirements of a message-driven bean
class:</p>
<ul><li><p>It must be annotated with the <tt>@MessageDriven</tt> annotation if it does not use a deployment descriptor.</p></li>
<li><p>The class must be defined as <tt>public</tt>.</p></li>
<li><p>The class cannot be defined as <tt>abstract</tt> or <tt>final</tt>.</p></li>
<li><p>It must contain a public constructor with no arguments.</p></li>
<li><p>It must not define the <tt>finalize</tt> method.</p></li></ul>
<p>It is recommended, but not required, that a message-driven bean class implement the
message listener interface for the message type it supports. A bean that supports
the JMS API implements the <tt>javax.jms.MessageListener</tt> interface.</p><p>Unlike session beans and entities, message-driven beans do not have the remote or
local interfaces that define client access. Client components do not locate message-driven beans
and invoke methods on them. Although message-driven beans do not have business methods,
they may contain helper methods that are invoked internally by the <tt>onMessage</tt> method.</p><p>For the Application Server, the <tt>@MessageDriven</tt> annotation typically contains a <tt>mappedName</tt> element that
specifies the JNDI name of the destination from which the bean will consume
messages. For complex message-driven beans there can also be an <tt>activationconfig</tt> element containing <tt>@ActivationConfigProperty</tt>
annotations used by the bean. See <a href="bncgw.html">A Java EE Application That Uses the JMS API with a Session Bean</a> for an example.</p><p>A message-driven bean can also inject a <tt>MessageDrivenContext</tt> resource. Commonly you use this
resource to call the <tt>setRollbackOnly</tt> method to handle exceptions for a bean that
uses container-managed transactions.</p><p>Therefore, the first few lines of the <tt>SimpleMessageBean</tt> class look like this:</p><pre>@MessageDriven(mappedName="jms/Queue")
public class SimpleMessageBean implements MessageListener {
    @Resource
    private MessageDrivenContext mdc;
    ...</pre>

<a name="bnbpp"></a><h4>The <tt>onMessage</tt> Method</h4>
<a name="indexterm-2147"></a><a name="indexterm-2148"></a><a name="indexterm-2149"></a><p>When the queue receives a message, the EJB container invokes the message listener
method or methods. For a bean that uses JMS, this is the
<tt>onMessage</tt> method of the <tt>MessageListener</tt> interface.</p><p>A message listener method must follow these rules:</p>
<ul><li><p>The method must be declared as <tt>public</tt>.</p></li>
<li><p>The method must not be declared as <tt>final</tt> or <tt>static</tt>.</p></li></ul>
<p>The <tt>onMessage</tt> method is called by the bean&rsquo;s container when a message has
arrived for the bean to service. This method contains the business logic that
handles the processing of the message. It is the message-driven bean&rsquo;s responsibility to
parse the message and perform the necessary business logic.</p><p>The <tt>onMessage</tt> method has a single argument: the incoming message.</p><p>The signature of the <tt>onMessage</tt> method must follow these rules:</p>
<ul><li><p>The return type must be <tt>void</tt>.</p></li>
<li><p>The method must have a single argument of type <tt>javax.jms.Message</tt>.</p></li></ul>
<p>In the <tt>SimpleMessageBean</tt> class, the <tt>onMessage</tt> method casts the incoming message to a
<tt>TextMessage</tt> and displays the text:</p><pre>public void onMessage(Message inMessage) {
    TextMessage msg = null;

    try {
        if (inMessage instanceof TextMessage) {
            msg = (TextMessage) inMessage;
            logger.info("MESSAGE BEAN: Message received: " +
                msg.getText());
        } else {
            logger.warning("Message of wrong type: " +
                inMessage.getClass().getName());
        }
    } catch (JMSException e) {
        e.printStackTrace();
        mdc.setRollbackOnly();
    } catch (Throwable te) {
        te.printStackTrace();
    }
}</pre>
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